ISO 13503-2 Proppant Crush Test for Hydraulic Fracturing and .

ISO 13503-2 has followed the work of the American Petroleum Institute (API), the original organization for standard testing hydrofracking. API RP-56, API RP-60, and API RP-61 testing standards were used to determine properties of proppants used in hydrofracking. In 2001, API and ISO members formed a group to create.